There are a number of machines, for example as shown in U.S. Pat. Nos. 3,453,801 and 3,553,059, assigned to the assignee of the present invention, which operate to wrap articles in an open ended generally tubular wrapper of heat shrinkable plastic film, herein sometimes referred to as a sleeve wrapper. In many installations, the sleeve wrapped articles are passed through a shrink tunnel without first closing the ends of the sleeve wrapper, and this produces a shrink-film wrapper which snugly engages the article but which has openings at the ends. It is desired in some applications to provide shrink-film wrappers that are closed on all sides and several different systems have heretofore been proposed for closing the ends of the open-ended wrapper prior to heat shrinking.
Some machines such as disclosed in U.S. Pat. Nos. 3,191,356 and 3,643,396 close the ends of the open-ended wrapper by pressing the upper and lower end portions of the wrapper into face-to-face contact, and then sealing the contacting faces and trimming the excess material from the wrapper. Such apparatus use wrapping material which is substantially wider than that which would otherwise be required to merely cover the top and ends of the article. Moreover, such apparatus usually require an additional trimming operation with the attendant problems of removing the trimmed material, in order to provide a neat package.
It has also been proposed, for example as shown in U.S. Pat. No. 3,739,547, to use stationary plows to fold the ends of an open-ended wrapper into overlapping relation at the ends of the article while the articles are advanced past the plows. While stationary plows work quite well with wrappers formed of relatively stiff material such as paper, difficulties are encountered when attempts are made to use stationary plows for folding relatively thin and flimsy plastic material such as is commonly utilized in shrink-film wrapping. Such thin and light weight plastic films tend to cling to the stationary plows as the articles are advanced past the plows and this causes numerous irregular folds and creases to be formed in the projecting ends of the sleeve material. The creases and folds in the ends of the wrapper not only adversely affect the appearance of the package, but also make it difficult to reliably seal the overlapping portions of the film together.